Houyi Ma

Inhibition of copper corrosion by several Schiff bases in aerated halide solutions

The inhibitive action of three Schiff bases, N,N′-o-phenylen-bis(3-methoxysalicylidenimine) (V–o-Ph–V), N,N′-p-phenylen-bis (3-methoxysalicylidenimine) (V–p-Ph–V) and N-[(2-hydroxy-3-methoxyphenyl)methylene]-histidine (V-His), on copper corrosion in aerated 0.5 mol dm−3 NaCl and NaBr solutions was investigated using EIS and steady-state polarization techniques. The inhibitor effectiveness depended strongly on the geometric structure of the Schiff bases. Among the three kinds of Schiff base used, the inhibition efficiency of V–o-Ph–V on copper corrosion was the highest, V–p-Ph–V the next and V-His the lowest. The Schiff bases inhibited the cathodic current more significantly than the anodic current. The different influences of V–o-Ph–V or V–p-Ph–V on the anodic and cathodic reactions led to the appearance of a low frequency capacitive loop in the impedance spectra. The inhibition action of the Schiff bases was due to their adsorption on the copper surface followed by complexation with Cu(I) or Cu(II) ions, forming a blocking barrier to copper corrosion.

Some aspects of quantum chemical calculations for the study of Schiff base corrosion inhibitors on copper in NaCl solutions

Abstract The inhibiting effect of some Schiff bases—N,N′- o -phenylen- bis (3-methoxy-salicylidenimine) (V–oph–V), N-2-hydroxyphenyl-(3-methoxy-salicylidenimine) (V–bso), N-4-phenylcarbazide-(3-methoxy-salicylidenimine) (V–psd) N,N′- o -phenylen- bis (salicylidenimine) (S–oph–S), N,N′- p -phenylen- bis (salicylidenimine) (S–pph–S), N-4-phenylcarbazide-(salicylidenimine) (S–psd) on the corrosion of copper in 1.0xa0M NaCl solutions, under various conditions, has been studied by means of the potentiostatic polarization method and the AC impedance technique. In order to study the ability of quantum chemistry to select corrosion inhibitors, quantum chemical calculations have been applied to the six kinds of Schiff base. The corresponding structures have been optimized and the energies and coefficients of their molecular orbitals have been calculated using the semi-empirical MINDO/3 method. The theoretical results obtained have been compared with the experimental data and the relations between the inhibition efficiency and quantum parameters (such as HOMO energy and LUMO energy) have been discussed.

Investigation on some Schiff bases as HCl corrosioninhibitors for copper

The inhibiting action of some Schiff bases on the corrosion of copper inhydrocholoric has been studied. The Schiff bases N, N′-p-phenylen-bis (3-methoxy-salicylidenimine) (V-pph-V), N, N′-o-phenylen-bis (3-methoxy-salicylidenimine) (V-oph-V), and N′-histidine-3-methoxy-salicylidenimine (V-his) were synthesized by reacting3-methoxy-salicylaldehyde with aromatic amines and histidine. The inhibiting action of theseSchiff bases has been studied on the corrosion of copper in 5% HCl solution. The potentiostaticpolarization and AC impedance studies reveal that all the studied Schiff bases inhibit thecorrosion of copper in the solution and that the inhibiting efficiency increases with a decrease intemperature or an increase in concentration of the Schiff base. The Schiff base of V-pph-V at aconcentration of 10−3 mol⧸dm3 can give 99.4% inhibition efficiency at 20°C.

Corrosion of stainless steels in acid solutions with organic sulfur-containing compounds

Abstract The influence of the organic sulfur-containing compounds on the corrosion of ferrite and austenitic stainless steels in sulfuric acid was studied. The results showed that the anodic dissolution and self-corrosion of stainless steels were remarkably accelerated in solutions with a low amount of the organic sulfur-containing compounds (0.02 mmol/dm3). With an increase of the organic sulfur-containing compound concentration, more and more the organic sulfur-containing compound molecules adsorbed on the electrode surface and segregated the metal surface from the solution, which caused the decrease of the anodic dissolution and hydrogen evolution current of stainless steels. The anodic polarization behaviors of stainless steels were also changed with the various types of the organic sulfur-containing compounds and stainless steels.

An ac impedance study of the anodic dissolution of iron in sulfuric acid solutions containing hydrogen sulfide

Abstract The anodic dissolution of iron in sulfuric acid solutions with H 2 S was investigated by means of ac impedance and steady-state polarization curves. The results show that H 2 S can accelerate markedly both the anodic dissolution and cathodic hydrogen evolution in most cases, but it can also exhibit a strong inhibiting effect upon iron dissolution under certain special conditions. Usually, the Nyquist diagrams measured at lower positive potentials consist of two overlapping capacitive loops, one of which is a characteristic capacitive loop caused by the adsorption of H 2 S on the electrode surface. At higher positive potentials, the original characteristic low frequency capacitive loop disappears, and the complex plane impedance diagrams for the iron electrode consist of an inductive loop and a capacitive loop. Based on the impedance behaviour of iron in the presence of H 2 S, two reaction models were proposed to interpret its dissolution mechanism in acidic solutions with H 2 S.

Protection of copper corrosion by carbazole and N-vinylcarbazole self-assembled films in NaCl solution

Self-assembled films of carbazole (CZ) and N-vinylcarbazole (NVC) were prepared on copper surfaces. The corrosion protection abilities of the films were evaluated in an air-saturated 0.5 mol dm−3 NaCl solution using electrochemical impedance spectroscopy (EIS), polarization and cyclic voltammetry. The results indicate that CZ and NVC form dense protective films on copper. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the film. It was found that the NVC molecules are tilted at an angle to the copper surface. The theoretical ab initio calculations support the experimental results.

Electrochemical behaviour of chromium in acid solutions with H2S

Abstract The electrochemical behaviour of chromium in acid solutions with hydrogen sulfide (H 2 S) was studied by the potentiostatic polarization method and A.C. impedance technique. Results show that H 2 S can remarkably accelerate both the anodic dissolution and the hydrogen evolution reaction. However, it has almost no influence on the passive state of chromium and cannot cause the breakdown of the passive film of chromium. The Nyquist impedance diagrams of chromium have been changed in size and shape by H 2 S. An anodic dissolution mechanism for chromium in acid solution with H 2 S was proposed to explain the obtained results.

Current oscillations during electrodissolution of iron in perchloric acid solutions

shandong univ, dept chem, jinan 250100, peoples r china. state key lab corros & protect, shenyang 110015, peoples r china.;chen, sh (reprint author), shandong univ, dept chem, jinan 250100, peoples r china

Synthesis of Silver Nanoparticles in Ionic Liquid by a Simple Effective Electrochemical Method

A simple effective electrochemical method was employed to synthesize large-sized anisotropic hexagonal and simultaneously smaller isotropic monodispersed spherical Ag nanoparticles in an ionic liquid. The electrolytic time was shortened remarkably, the dosage of stabilizers was much lowered and mechanical stirring can be needless when ionic liquid was used as a substitute for water in the electrolytic reaction.

The Effect of Reversed Micellar Systems on the Catalytic Activity of Monodisperse Catalysts III, Studies on the Hydrogenation Activity of Cobalt Boride Particles in the CTAB/1-HexanoI/Water Reversed Micellar System

Abstract Despite the fact that the monodisperse cobalt boride particles prepared in CTAB / 1-hexanol / water reversed micellar systems are the quite small particles with a narrow size distribution, they exhibited little hydrogenation activity in reversed micellar solution. The chief cause are due to combined effect of both adsorption of the CTAB molecules on the catalyst and the slow transport process of hydrogen from the organic phase of the reversed micellar solution to the surface of catalyst. The experiments have revealed an interesting fact that addition of ethanol to the reversed micellar solutions simultaneously lead to the increase in catalytic activity and coagulation of catalyst particles.